Newt Gingrich's campaign bus pulled out of town a few minutes earlier, and Mathisen, 61, could have easily blended in with the crowd of Republicans who showed up to see the candidate at a Coca-Cola bottling plant.

Mathisen, though, is a Democrat and supported Obama in 2008.

"I just wish I hadn't have done it," he lamented Saturday, explaining he thought the president overreached on health care and did not bring U.S. troops home from Iraq soon enough.

"I'm not impressed with him," he added, "but I'm not that dissatisfied."

The conflicted feelings are evident across Iowa, which had a crucial role in putting Obama in the White House with his come-from-behind victory here four years ago.

The importance of this first-in-the-nation nominating contest is often overstated, but on that night, in a state that is overwhelmingly white, a record turnout helped propel a black man to the presidency.

"They said this day would never come," Obama proclaimed in Des Moines.

But on the eve of a new caucus, when voters will help determine the Republican to face Obama, Iowa Democrats are reassessing their legacy. They wonder if Obama was experienced enough and had the tenacity to confront America's woes, or whether they should have attempted to mint the first female president.

"Hillary would have been more prepared for all the problems with her experience," said Tom Baccam, 45, of Des Moines, referring to Hillary Rodham Clinton.

Woodward, a farmer and mail carrier, caucused for Obama because of his uplifting message of change. Despite his reservations about him now, Woodward said he will vote for Obama again, if only because he's uninspired by the Republican candidates.

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The president seems acutely aware of the mixed feelings here and is fighting to change them. While the focus has been on the Republican candidates traversing the state, each trying to be the loudest Obama critic, an undercover army is growing for the general election in November.

Obama has eight offices here — more than any of the Republicans — and volunteers have made more than 350,000 calls. Tuesday night, volunteers will try to turn out people for their own caucuses, which will serve as a practice run for November. Obama will deliver a live message via video.

"No matter what happens on Jan. 3 … one thing is for sure: On Jan. 4, we will have the strongest campaign infrastructure and grass roots organization in place of any candidate going forward," said John Kraus, Obama's Iowa campaign spokesman.

The effort in a state of just over 3 million people — replicated in bigger swing states like Florida, North Carolina and Ohio — reveals Obama's strategy to spread his chances across the electoral map. Iowa has only six electoral votes, but Obama will likely need them to keep his job.

He defeated John McCain in Iowa by nine points in 2008; this time no one expects to win the state that easily.

So it was little coincidence that Obama made a swing through Iowa in mid August as part of a White House bus tour to rally support for his economic ideas and rail against a deadlocked Congress.

"I don't care whether you're a Democrat, a Republican, or an independent, all of us are patriots, and everybody here cares about our country and puts it first. If we can have that kind of politics, then nothing can stop us," Obama said in Decorah, standing before a picturesque red barn.

The following morning he ate eggs and toast at a restaurant in Guttenberg, nestled along the Mississippi River, while speaking with small business owners.

"He walked into a mess," Sue Rausch, owner of Rausch's Cafe, said in an interview last week. "He's trying his hardest to resolve some of the issues, but four years isn't long enough."

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Four years ago, Obama was locked in a bitter struggle for the Democratic nomination with John Edwards and Clinton. Iowa seemed poised to coalesce behind Clinton, who had the ingredients for a win: name recognition, money and the backing of Iowa's powerful labor unions.

But Obama outworked her. Youthful volunteers poured into the state to galvanize an expertly organized field operation. He was a fresh presence, and his optimistic message generated excitement and momentum. On caucus night, the country was shocked by his decisive victory.

Clinton's inevitability was broken.

"It was really nice to see we jump-started the president," said Devin Jacobsen, a University of Iowa senior who was 18 at the time and participating in his first caucus. "People have been saying he hasn't followed through, but he has for a majority of it."

Enthusiasm for Obama among Jacobsen's peers has fallen off nationally, however. Many college graduates have struggled to find jobs and face significant college loans. They have grown frustrated with the lack of action in Washington due to the partisanship Obama pledged to transcend.

Obama will need to recapture that support as part of his overall coalition.

"He's gone a little bit softer than I'd like him to," said Cassie Creasy, 23, of Coralville, who was a student leader for Clinton. Creasy contends Obama gave too much ground to Republicans on health care. "But he needs to compromise, or I think a lot less would have gotten done.

"I've had a lot of people say to me, 'I wish it would have been Hillary. Things would have been different.' But by the same token, if she were elected, people would have been saying the same things about Obama."

Polls in Iowa confirm Obama's challenge, with him running about even with Mitt Romney and Gingrich, who had been a leading contender until slipping in recent days. An NBC News/Marist survey released Friday showed voters are also evenly split on whether they approve of the job that Obama is doing.

"There's no question about it, it's going to be an extremely tough election," said Roxanne Conlin, a lawyer in Des Moines who co-chaired Edwards' campaign in 2008.

She has felt the Obama sting herself, attributing her unsuccessful 2010 U.S. Senate bid to his sliding popularity.

"It was a terrible Democratic year. The regret of Barack Obama was principally responsible for that."

Nonetheless, she thinks that Obama's base will rally around him and that independents, who flocked to the GOP in 2010, will understand the challenges Obama has faced since voters here propelled him into office.